How would I go about using mental ray in houdini? I see that it is somewhat built in, but not included in the package. Is there a way to test it out? I have mental for use in Maya and Max, can I use the standalone from those packages with houdini?

Yes, you can only use the standalone ray executable. Simply lay down a mentalray ROP, point to the executable and fire away.

btw. You must configure the necessary environment var (MI_ROOT) that points to the config file .rayrc with shaders.

thanks diula. the environment variable part was the key.

Hello Diula,

I also would like to use Mental Ray, but your explainations are a bit fast for me
- How do you specify the executable to the MR ROP?
- Where is located the MI_ROOT variable?

Can you please add some details?

Thank you very much

You specify the executable in the ROP parameter Command (or sth likethat, don't have H in front of me now). Simply choose the executable ray3 from the file picker.

As for the MI_ROOT thing, this is an environment variable which is queried by the ray executable on startup. It points to a directory that must contain the mental ray configuration file - .rayrc. In the file itself are all the shader declarations, and possibly some default startup options. If you have mental ray standalone purchased through Avid or Autodesk (as far as I can remember) the MI_ROOT environment was set through a batch file. So, assuming you have an installed mental ray, you should also have a rayrc (or ray3rc) file. Simply create an environment variable and specify the directory where the file is.

envi. var. are located in XP by:
controlPanel>systemProperties>Advanced>EnvironmentVariables

just in case.

There is a little info on what Environment Variables mean to Houdini here:

http://odforce.net/wiki/index.php/CustomizingHoudini [odforce.net]


(This info could be expanded on, but its a start)

This site is always a great resource. I have to get in the habit of checking it out when I have a problem.

Hum, I only have 3dsMax installed, and I suppose I can use the MR version it provides. It is a satelite, does it make a differece?

You specify the executable in the ROP parameter Command (or sth likethat, don't have H in front of me now). Simply choose the executable ray3 from the file picker.

Ok, so iIused the following file in H:
“C:\3dsmax8\mentalray\satellite\raysat_3dsmax8.exe”

I defined the MI_ROOT path in the environment variables to the same folder, because the rayrc file is in it.

The MR render node in H stays red. I also tried to put the content of the rayrc from the folder right above this one (because there are 2 such files in Max), and still red.

- Are the shader descriptions refenreced by that file only for 3dsMax?
- there are already some shader nodes for MR in H, how are they linked to MR if the declarations are provided by the user?
- is there a log in H saying that something went wrong and why the node cannot be used?

Thank you

If you MMB on a node you'll see some info. When it's red, you'll get the reason why it has failed.

I think that the Max satellite mental ray does have customized commands. But since you can export .mi files from Max there has to be a way.